1. Technical Field
The present invention relates to an ink for forming a functional layer, a method of manufacturing an ink for forming a functional layer, and a method of manufacturing an organic electro-luminescence element.
2. Related Art
As a method of forming a functional layer by using a solution including a functional layer forming material as an ink and applying the solution onto a film forming region to be solidified, a liquid droplet discharging method using an ink jet head capable of discharging an ink from a nozzle as a droplet is employed. By using the liquid droplet discharging method, it is possible to accurately arrange an ink with a required amount as a droplet in the film forming region and form a stable functional layer in a film shape.
As an example of the functional layer formed by such a liquid droplet discharging method, a wiring layer, a semiconductive layer, a coloring layer in a color filter, a luminescence layer in a luminescence element, and the like are included.
When foreign substances (particles) are included in the solution (ink) including the functional layer forming material, the functional layer is formed in a state in which the foreign substances (the particles) are included in the film forming region, and thus a part in which an original function can not be obtained in the functional layer is generated.
Therefore, for example, in JP-A-2007-95516, an application liquid which is used when at least one layer among organic luminescence medium layers is formed by a wet film forming method and produced by dissolving or dispersing a forming material in a solvent, in which the number of particles of 0.5 μm or more included in the application liquid is 50 pieces/ml or less, is indicated.
In addition, for example, in JP-A-2013-26164, a method of manufacturing an organic electro-luminescence ink composition including a process of pressure-filtering a solution produced by dissolving a high molecular organic electro-luminescence material in an organic solvent with a filter having a hole diameter from 0.03 μm to 0.1 μm is disclosed. According to Example described in JP-A-2013-26164, even if the hole diameter of a filter is set to 0.05 μm, and the filtering pressure and the filtering speed are adjusted, the number of particles of 0.5 μm or more included in 10 ml of the organic electro-luminescence ink composition is 10. When converted into the number of particles in 1 ml of the ink composition, the number of particles of 0.5 μm or more is 1.
However, in a display apparatus having an electrically independent organic electro-luminescence element for each pixel, even if one layer among the organic luminescence medium layers is formed using the application liquid in JP-A-2007-95516 and the organic electro-luminescence ink composition in JP-A-2013-26164, the pixels including the foreign substances are easily counted as a defect when the size of a pixel which is the film forming region becomes fine. That is, there was a problem in which it becomes difficult to manufacture the display apparatus in good yield.